Open‐path, near‐infrared tunable diode laser spectrometer for atmospheric measurements of H2O

A new instrument for in situ measurements of atmospheric water vapor from aircraft platforms has been developed based upon near-infrared turnable diode laser sources operating near 1.37 μm. The spectrometer features a unique open-path, multipass (Herriott) cell for true in situ monitoring of water vapor concentrations with precision levels exceeding those of existing Lyman α and frost point hygrometers. External sampling outside of the aircraft boundary layer minimizes ambiguities in the measured water vapor abundances. Variable spectrum acquisition rates up to 10 Hz provide fast temporal resolution free from sampling or flow rate limitations. In its current configuration the instrument operates from the right wing pod of the NASA ER-2 research aircraft and is optimized for measurements in the upper troposphere and stratosphere (to 20 km). Measurement precision is ±0.05 ppmv in the stratosphere for a 2-s measurement integration period. The flight-ready instrument weight is 8.2 kg, and power consumption, exclusive of structural heaters, is 7.5 W.

[1]  S. Oltmans,et al.  Increase in lower-stratospheric water vapour at a mid-latitude Northern Hemisphere site from 1981 to 1994 , 1995, Nature.

[2]  Thomas F. Hanisco,et al.  Aircraft-borne, laser-induced fluorescence instrument for the in situ detection of hydroxyl and hydroperoxyl radicals , 1994 .

[3]  R. May,et al.  Data processing and calibration for tunable diode laser harmonic absorption spectrometers , 1993 .

[4]  James M. Russell,et al.  The Halogen Occultation Experiment , 1993 .

[5]  D. Rind,et al.  Annual variations of water vapor in the stratosphere and upper troposphere observed by the Stratospheric Aerosol and Gas Experiment II , 1993 .

[6]  Syukuro Manabe,et al.  Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity , 1967 .

[7]  W. Read,et al.  Upper tropospheric water vapor and cirrus: Comparison of DC‐8 observations, preliminary UARS microwave limb sounder measurements and meteorological analyses , 1996 .

[8]  R A Toth,et al.  Extensive measurements of H216O line frequencies and strengths: 5750 to 7965 cm(-1). , 1994, Applied optics.

[9]  SURFACE ACOUSTIC WAVE MICROHYGROMETER , 1997 .

[10]  R. May,et al.  Simultaneous in situ measurements and diurnal variations of NO, NO2, O3, jNO2, CH4, H2O, and CO2 in the 40‐ to 26‐km region using an open path tunable diode laser spectrometer , 1987 .

[11]  K. Kelly,et al.  Wintertime asymmetry of upper tropospheric water between the Northern and Southern Hemispheres , 1991, Nature.

[12]  E. Weinstock,et al.  New fast response photofragment fluorescence hygrometer for use on the NASA ER‐2 and the Perseus remotely piloted aircraft , 1994 .

[13]  C. Weitkamp,et al.  Two-mirror multipass absorption cell. , 1981, Applied optics.

[14]  John C. Gille,et al.  The Limb Infrared Monitor of the Stratosphere: Experiment Description, Performance, and Results , 1984 .

[15]  M. Newchurch,et al.  Seasonal variations of water vapor in the lower stratosphere inferred from ATMOS/ATLAS-3 measurements of H2O and CH4 , 1996 .

[16]  M. Newchurch,et al.  ATMOS Measurements of H2O + 2CH4 and Total Reactive Nitrogen in the November 1994 Antarctic Stratosphere: Dehydration and Denitrification in the Vortex , 1996 .

[17]  W. Read,et al.  Walker circulation and tropical upper tropospheric water vapor , 1996 .

[18]  L. Heidt,et al.  A comparison of ER-2 measurements of stratospheric water vapor between the 1987 Antarctic and 1989 Arctic Airborne missions , 1990 .

[19]  R. May,et al.  Aircraft (ER-2) laser infrared absorption spectrometer (ALIAS) for in-situ stratospheric measurements of HCI, N(2)O, CH(4), NO(2), and HNO(3). , 1994, Applied optics.

[20]  K. Kelly,et al.  Water vapor and cloud water measurements over Darwin during the STEP 1987 tropical mission , 1993 .

[21]  J. Russell,et al.  Estimates of the water vapor budget of the stratosphere from UARS HALOE data , 1996 .

[22]  S. Wofsy,et al.  Emission Measurements of the Concorde Supersonic Aircraft in the Lower Stratosphere , 1995, Science.

[23]  D. Rind,et al.  Intercomparison of stratospheric water vapor observed by satellite experiments: Stratospheric Aerosol and Gas Experiment II versus Limb Infrared Monitor of the Stratosphere and Atmospheric Trace Molecule Spectroscopy , 1993 .

[24]  S. W. Bowen,et al.  In situ observations in aircraft exhaust plumes in the lower stratosphere at midlatitudes , 1995 .

[25]  Richard B. Rood,et al.  Upper-tropospheric water vapor from UARS MLS , 1995 .

[26]  Wesley A. Traub,et al.  Validation of measurements of water vapor from the Halogen Occultation Experiment (HALOE) , 1996 .

[27]  James M. Russell,et al.  Hemispheric asymmetries in water vapor and inferences about transport in the lower stratosphere , 1997 .

[28]  Herwig Kogelnik,et al.  Off-Axis Paths in Spherical Mirror Interferometers , 1964 .

[29]  R. Jones,et al.  Is water vapour understood? , 1991, Nature.

[30]  J. Pyle,et al.  Active nitrogen partitioning and the nighttime formation of N2O5 in the stratosphere: Simultaneous in situ measurements of NO, NO2, HNO3, O3, and N2O using the BLISS diode laser spectrometer , 1990 .

[31]  R. May.  Response function of a tunable diode laser spectrometer from an iterative deconvolution procedure , 1988 .

[32]  M. Loewenstein,et al.  SPADE H2O measurements and the seasonal cycle of stratospheric water vapor , 1994 .

[33]  S. Oltmans,et al.  Simultaneous balloonborne measurements of stratospheric water vapor and ozone in the polar regions , 1991 .

[34]  J. A. Silver,et al.  Frequency modulation and wavelength modulation spectroscopies: comparison of experimental methods using a lead-salt diode laser. , 1992, Applied optics.

[35]  John C. Gille,et al.  Validation of water vapor results measured by the Limb Infrared Monitor of the Stratosphere Experiment on NIMBUS 7 , 1984 .